The present invention relates to a universal glenoid component for a shoulder prosthesis and to a method for implanting such component which will minimize the amount of bone structure required to be removed from the scapula.
In the implantation of a glenoid prosthesis in a scapula, it is desirable that as little of the bone material forming the neck of the scapula as possible be removed when the scapula is prepared to receive the glenoid component. In preparing the scapula to receive a glenoid component, a cavity is formed primarily in the neck of the scapula in which the glenoid component may be positioned, either directly in the cavity if the glenoid component is of the type intended for use without bone cement or implanted in bone cement if the glenoid component is of the type intended to be held in place by bone cement. In either event, it is desirable to remove as little bone structure from the scapula as possible in preparing the scapula to receive the glenoid component.
Prior art shoulder replacement prosthesis disclose many different procedures and different shapes of glenoid components of total shoulder prostheses which require removal of extensive amounts of bone from the scapula in preparing it to receive a glenoid component.
For example, U.S. Pat. No. 4,550,450 (incorporated herein by reference) discloses a total shoulder prosthesis system having a glenoid component 12 with a fixation keel 27 projecting rearwardly from base member 26 for fixation into the cancellous component of the scapular neck. The fixation keel 27 along with the enlarged surface of the base member 26 from which the fixation keel 27 extends and the provision of a coracoid notch 29 on such side of the base member 26 requires removal of the natural glenoid surface from the scapula as is readily seen in FIG. 1 of such patent.
Similarly, U.S. Pat. No. 4,964,685 (incorporated herein by reference) requires resecting the glenoid cavity to provide a flat resected surface against which the flat medial surface of the glenoid component rests. The bone of the scapula 130 is resected in an amount substantially equal to the height of the side walls 40 of the prosthesis to provide a flat resected surface 146. Additionally, two peg holes 142, 143 are drilled into the tissue 139 of the scapula 130 with the result that significant amounts of bone tissue are removed from the patient in preparation for implantation of the glenoid component.
U.S. Pat. No. 4,261,062 shows a natural shoulder joint prosthesis having a glenoid component with an elliptical configuration and a tapered keel 36 having a series of transversely extending ribs 40, 42, and 44.
U.S. Pat. No. 4,865,605 discloses a modular shoulder prosthesis having a glenoid component 30 with a stem 37 extending from a flat surface of the base 33 for implanting in a prepared cavity of the scapula.